I have used SunnySky X2212/980(ish.. or 920, cant remember) on similar build and had the feeling of not having enough power to controllably spin 10" (yet alone 12" which I have also optimistically tried ). That was also using 3S/5000.

If you fly the f450 without any addons, configured like in the link above (my config ;-) ) then you have enough power to go straight up to the stars ;-) if you put all the stuff on this poor little thing its getting much weaker...but its really good for taking videos...just be sure to set your pids really smooth...and be sure to fix all motor connections proberly if you use these standard motor connections plugs..also be sure that all connections to the controller are fixed very very good...especially gps and mag connections...and use ccw and cw motors...etc etc